COURSE of the MONTH

SQL Server long running query

I have a query that is taking a long time i think it may ahve to do with the not in statement. please see below(this is customer logon info):
select rtrim(Cast(Datepart(mm, Date)as char)) + '/' + cast(DatePart(yyyy,Date) as char), count(distinct(ID)) from ActSrv_2007 WITH (NOLOCK)